No Ersatz

By Ernest Bruce
Chief Engineer, Vultee Aircraft, Inc

An American engineer looks at a German Messerschmitt

On Apr 1, a Messerschmitt 110 fighter plane arrived in Los Angeles harbor aboard the freighter Montanan, consigned to the Vultee aircraft factory from the British Air Ministry. Vultee engineers, and others as well, have now had an opportunity of making a preliminary examination of this interesting plane. This report is based on a more or less casual inspection of the plane as received at our plant. In attempting to present an examination of this famous fighter plane it is important to call the reader's attention to the fact that this type is actually now obsolescent, having first been flown in 1937, so that it does not necessarily represent the very latest practice in German design and construction.

An engineer's first impression of the Messerschmitt is that it is a thoroughly workmanlike machine, and this is borne out by close inspection. A surprising thing is how a crew of three men have been fitted into such a small airplane. In size and general arrangement the 110 compares closely with the Lockheed P-38. Span and weight are a little greater, as is the horsepower, while performance is somewhat lower. The Messerschmitt of this model is thought to have a top speed of about 365 mph, which would be about 40 mph slower than the export version of the P-38. The crew of three men in the 110 are accommodated in tandem arrangement in a relatively narrow, but deep fuselage. The pilot is forward, of course, and has unusually good vision for a twin-engined plane. The rear gunner has a single pedestal-mounted machine gun one of the plane's few obvious weak spots; while the radio operator is located in the center where he can also service the two belly-mounted cannon.

Perhaps it will help if we first dispose of the armor and armament question before considering the detailed design and construction of the plane. While the two fuel tanks and the oil tanks are of self-sealing construction, it came as something of a surprise to find that the 110 is not armored anywhere. What the plane lacks in armor, however, it makes up in forward armament. There are four 7.3-mm (approximately .30 caliber) machine guns mounted in the upper nose of the fuselage in fixed position. We would guess that these four guns, firing along the line of flight, might just about match the effectiveness of the British Spitfire eight-gun installation since the latter arrangement results in a fire dispersion which somewhat reduces effective range. But the real fire power of this plane lies in the two aircraft cannon, of 20 mm, mounted in the belly where the shock of firing can be transmitted directly to the heaviest part of the structure. Long steel blast tubes run forward a distance of about 5 ft (from the gun muzzles) to the nose cowl opening. These two cannon, firing together, have proved most effective against targets both in the air and on the ground. In Poland these planes are said to have disabled railroad engines with fire from their cannon. And their effectiveness in aerial combat over England is indicated by the fact that the British are now mounting cannon on their fighters. It is not hard to picture the effect from a burst of fire at close range from all six forward guns of the 110, four machine guns and two cannon. But this forward power is gained by sacrificing rear protection, both in armor and armament. The single gun provided at the rear would be a poor match for any fighter which got in position for a burst. This rear gun is not well located or mounted, so that it covers a limited field of fire and seems to have been an afterthought. With the Messerschmitt's rear thus left so highly vulnerable it must be concluded that the designers of this machine relied on superior speed for protection. Against the British Spitfire this has doubtless proved to be a serious miscalculation.

Since no twin-engine plane is likely to stand up to a first-class single-engine pursuit in a dog fight, the Me-110 must be regarded as a hit and run weapon. It possesses deadly power for a single forward burst, but if that does not destroy the opponent it must then run for its life. Since the Me-110 is also used as an attack bomber it is fitted with external bomb racks under the fuselage and wings and particularly on short-range missions could carry an effective load of bombs.

Aerodynamically the Me-110 leaves little to be desired. Fuselage and nacelles are of highly efficient form. A remarkable feature is the manner in which size has been kept down without cramping accommodations or restricting accessibility. The twin-rudder tail is conventional. Exterior finish is extremely smooth all over, with flush riveting throughout. No projections are permitted to spoil the smooth surface of the machine and it is doubtless of a high order of efficiency. Both slots and flaps are provided, the flaps being of full-trailing-edge type, extending between fuselage and ailerons. Wings have a span of 55 ft, an area of 414 sq ft, and aspect ratio of 7.3 to one. The taper ratio is not more than two to one. The wing tips are blunt and almost straight, but appear to be efficient, especially from the standpoint of stall control.

Completely disrupting the story about meager instrument equipment on Nazi planes, this ship has a very line set of instruments and complete radio equipment. One item of instrument equipment is well in advance of our current practice, and that is the remotely mounted compass, which is situated back in the tail of the machine with an indicating dial on the pilot's instrument board. This feature doubtless helps to compensate the compass for large masses of steel represented by gun and engine installations. Radio equipment appears to be of the highest type, and the quality of German precision instruments is well known. The pilot is provided with an artificial horizon in addition to the turn and bank indicator. Tachometers, temperature and pressure gauges are provided for both engines. And the pilot has a sensitive rate of climb instrument in addition to standard altimeter and air speed indicators.

Installation of equipment and accessories and the general handling of plumbing and wiring throughout the machine is most praiseworthy. Everything is accessible to a degree which at least matches current American practice. All hydraulic lines are coded by color and direction of flow is indicated with arrows. Quickly detachable connectors are provided in all cases. Where items of equipment are not readily accessible from within the plane they are provided with large doors for easy accessibility from outside. The general attention paid to serviceability is well illustrated by the engine and wing mountings. The wings are each made in a single panel, attached to the fuselage structure by four fittings. These fittings are themselves easily accessible and simple. It would probably be but a few minutes work for a trained crew to remove both wings. When the wings are removed there is exposed against the outside of the fuselage a substantial portion of the control plumbing and wiring. This wiring, incidentally, is shielded throughout the plane, but no conduit is used. Shielded wires are simply hung in place along the structure by means of simple clips, resulting in complete accessibility for maintenance work. Throughout, simplified maintenance has been stressed.

The engines are mounted on the conventional forged magnesium alloy arms which are standard with most German planes. These free the engine compartment of complex structural members and provide for easy accessibility to all parts of the engine requiring routine servicing. Service doors in the engine cowl make it possible for the mechanic to reach all spark plugs or injection pump parts instantly.

Detailed structural design throughout the plane appears to have been dictated chiefly from a production standpoint. There is every evidence that this machine is assembled from component parts produced in a wide variety of shops. In fact it may well be that not all planes of this model are identical, for there is such a wide variation in the use of castings, forgings, welded fittings, etc., that it is conceivable that one plane might have a forged part of magnesium where another would have a welded steel tube or riveted aluminum alloy part for the same purpose. We do not know that this is the case, but we do know that the plane has been designed for rapid final assembly from component parts which might vary considerably in tolerances. This is illustrated in various ways. The wing root and tail fairings, for example, are attached by means of screws and washers in such a way that large attachment holes in fairing parts, plus the wide washers, make up for any variance from tolerances. The wing fittings are of special interest. Since the wing is of monospar design there are but two main attachment fittings, with two locating and stabilizing fittings fore and aft. The lower main fitting is a pin joint about which the wing may be swung vertically for dihedral adjustment, which is accomplished by two lock nuts on the threaded bolt projecting into the upper main fuselage fitting. This fitting has appreciable "slop" or looseness laterally which permits the wing incidence to be set at the fore and aft locating fittings. These have location blocks with horizontal serrations, permitting considerable horizontal or vertical adjustment before bolting the blocks solidly in place. This same feature is found in many places throughout the plane where universal joints, or ball and socket joints provide for quick connections of parts without concern for close adjustment. This is also true of the engine mount attachment, which by means of universal joint connections allows a wide variance without causing strain or misalignment.

Nowhere in the construction of the 110 is there any evidence of hasty workmanship, "ersatz" materials, or substitution of any kind. Steel, aluminum, magnesium are all used in abundance, and there is quite a bit of rubber in the plane whether synthetic or natural. The tires, interestingly enough, are marked Made in Germany in three languages, including English, which may indicate they were originally manufactured for export. Steel is used for canopy framing, undercarriage parts, main spar structures across the fuselage and in numerous smaller applications. Magnesium forgings are used for various control arms, engine mount arms, etc. The bulk of the structure of both the fuselage and wings is of aluminum alloy sheet material. Structural design runs a little closer to the true monocoque than with most American skin-stressed planes. The skin of fuselage and wings is of comparatively heavy gauge and the structure is simplified considerably. The result is that the exterior surfaces are quite rigid, producing smooth contours which are probably of high aerodynamic efficiency as well as weather and wear resistant.

The fuselage construction is particularly interesting, partially because it is not apparent how the skin sections are formed. The fuselage is constructed in two halves, split along the top and bottom centerline. Sections run laterally rather than longitudinally. Forming rings largely were eliminated by forming a joggle and an open "C" flange at one edge of each skin section. This provides for flush joints and gives sufficient lateral stiffening without added internal support. Longitudinal stiffeners are rolled or drawn channel sections extending fore and aft through cut- outs in the open flanges mentioned above. Longeron members running past the cockpit section are apparently one-piece stampings of heavy sheet material. Throughout the plane every effort has been made to reduce the number of parts used, relying on simpler, larger, and heavier parts to carry the load.

For example, the wing is of extremely simple construction of monospar type. Actually the wing shell is the spar, with a single shear web installed at the point approximating center of lift. This web is a solid sheet which is riveted to simple angle flanges along top and bottom to form an "I" beam. These flanges, in turn, are riveted directly to the wing skin. This skin is laid on in large pieces extending fore and aft rather than spanwise. Ribs are not closely spaced and are built up of riveted sections. Spanwise skin stiffeners are also relatively few, since the thickness of the skin reduces the requirement for stiffening members.

One item of interest, and not fully explained to date, is the quick releasable tail cone. This part is of clamshell construction hung to the fuselage stern by three pins, one of which may be tripped by a cable to the cockpit. When the pin is tripped this cone flies off, and open, since it is hinged at the rear. It is surmised that a collapsible flotation bag, or life raft, is carried in this way for protection against water landings. An external retaining wire runs from the cockpit to the tail cone, probably as a means of hauling in the raft after a forced landing.

Engine cooling radiators are very cleanly installed. The oil cooler is in the nose of the engine nacelle, but each engine coolant radiator is located in the wing near the trailing edge, between the main spar and the flap. In this position the minimum drag is probably achieved for cooling flow obtained. Exhaust air can be controlled by means of an adjustable flap. Engine intake air is taken through a duct in the leading edge which is smoothly cowled and vaned for efficient air flow.

Engines are of Daimler-Benz type of 1,150 hp, and are supercharged. Fuel is injected into the cylinders but ignition is by conventional Bosch magnetos and two spark plugs per cylinder. Neither engine has been disassembled, but the external impression is one of extreme ruggedness and simplicity. VDM propellers, of three-blade type, are electromechanically controllable to full-feathering position.

Canvas shields, with zipper fastenings, protect a number of parts of the plane from dust and water. This is the case in the cockpit, which is well sealed against wind or air leakage. But there is no apparent provision for forced ventilation or heating of the crew's compartment. Nor is there any de-icer equipment provided on wings or propellers, nor any windshield wiper. Also the engine air intake looks susceptible to icing.

Wing flaps and the retractable landing gear appear to be hydraulically operated with pneumatic emergency control. The landing gear is simple and rugged, retracting the wheel straight back up into a wheel well in each engine nacelle.

Interestingly enough, engine exhaust stacks are simple elbows used to deflect the exhaust away from the engine radiator, and with no more than a limited attempt to employ the jet propulsion effect utilized by the British.

The engines on S9CK are rather oily, though this may be the result of the forced landing. In any case the machine shows signs of hard service in many ways and it is to be surmised that this particular plane had done a great deal of military flying of one kind or another before it was finally brought down in England, affording our designers a first-hand study.

Comparative Figures
(Export version of P-38)
(interceptor pursuit type.)
Me 110
(Convoy "Destroyer"
and light Attack Bomber.)
Length 37 ft 10 in 35 ft
Span 52 ft 55 ft
Gross weight 13,080 lb 14,800 lb
Wing area 327 sq ft 414 sq ft
Wing loading 40 lb/sq ft 35.7 lb/sq ft
Power 2,100 hp
(2 Allisons)
 2,300 hp
(2 Daimler-Benz)
Power loading 6.2 lb/hp 6.4 lb/hp
Speed 404 mph 365 mph
Range  600 mi 1,000 mi +
Service ceiling 30,000 ft + 30,000 ft +
Crew One Three
Armament 1 cannon
4 machine guns
 2 cannon
5 machine guns

This article was originally published in the June, 1941, issue of Aviation magazine, vol 40, no 6, pp 44-45, others; pages are missing from my copy; the article is taken from Aviation's Sketchbook of Design Detail, edition 1, pp 70-73.
The original article includes 5 photos and 3 detail drawings.
Photos are not credited, but are presumably from Vultee. They were probably vetted by the AAF.